PeachParts Mercedes-Benz Forum - Diesel misses when first started

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- - Diesel misses when first started (http://www.peachparts.com/shopforum/showthread.php?t=175991)

your on the right path now NEWER diesels start better In 1985 1983 diesels started better I dont start as well as I did either but I'm ok once I get going :)

Plugging them in warms the water and that warms the bore... so when the air goes into the bore it is not cooled as much and that certainly helps with ignition... particularly if everything is not perfect ( like fuel atomization on an old car ) ....

If it was missing, how were you able to get in to start it in the first place?
:wacko: :wacko:

...could'nt resist

Quote:

Originally Posted by 777funk (Post 1385000)

Hi guys,
I have a 300d (silver beaut!) that tends to miss a little bit when I first start. I think all the glow plugs are good. I test continuity in each. But it just sort of takes a second to get smoothed out (about 20 seconds of 2k rev). After that it's totally fine. Also, if I plug it in it starts smoothly. If I start it again within the next hour it's fine. Etc. basically if it's warm it's smooth. If a cold start (even on a 60 degree day) it's rough at first. Is this normal? Should I do anything about it?
Thanks for the advice!

I would most definitely start with a valve adjustment and you might want to consider doing a leakdown test. Yes, Diesels will run rough when started cold, but a miss when cold is usually a sign of out of adjustment valve train! There could be other reasons too, but this is where you should start since diesels are compression-ignition engines! Work your way forward from there. I'm inclined to lean toward a valve adjust as a first test since it should not miss on a 60 degree day. Check your glow plugs second. I hope this helps, keep us posted!! Fuel injectors, glow plugs,etc...:book: ;)

My old '87 300TD carried on the same way. I finally figured out it is oil leaking down the valve stems. Warm the block and that oil will leak past the rings and cause no problem, if it is, indeed, a problem.

My 190D starts smooth. I had the injectors flow matched and popped @ 150 bar and that solved alot of issues (smoking, skipping cold and nailing).

Well,
this was my first post I believe (a long time ago now:)).

I think with a little more diesel experience under my belt I've got it narrowed down.

That car's long gone but I have two more that had similar issues and it ended up being injection pump timing.

The chain wears (stretch) and the timing gets retarded. The dealer advanced my 87's timing 3 degrees (on time now) and it starts smoothly now.

I just did the same thing (slight pump advance) on my new 84 that wasn't starting dead smooth and now it fires right up.

Seems to me these old cars with original chains aren't getting proper injection timing. Obviously a new chain would most likely correct the problem. But I didn't want to put money into my rusty old 84 so I just adjusted the pump ahead about 1/16" or a tad more according to the nut's holding the IP on and it's good.